Gases are generated in landfills and can cause serious problems. Through the naturally occurring decomposition processes that occur within the waste contained in a landfill, a number of gaseous products are generated. These gaseous products, if allowed to migrate uncontrolled from a landfill, may result in dangerous conditions within buildings that the gas may enter. Uncontrolled release of the gas to the atmosphere may cause air pollution.
Solid waste initially decomposes aerobically, and the primary gas product is carbon dioxide. As the oxygen is depleted, anaerobic microorganisms begin to dominate. These bacteria continue to produce carbon dioxide, but additionally, produce methane. Additional compounds are produced, and additional chemicals are released into the landfill by volatilization.
Typically, landfills are covered by a combination capping system. This system can include a series of bentonite clays and a polymeric (typically polyvinyl chloride (PVC)) liner. This liner system has the purpose of containing landfill gas and odors. Landfill gas is collected under the liners and directed to vents that are vented to the atmosphere. These vents are equipped with flares to bum off the gas in order to prevent odor problems.
The dilemma with this method of disposal of landfill gas is that one problem (the flaring of landfill gas produces noxious by-products) is exchanged for another (the migration of untreated landfill gas into the atmosphere). This invention is directed to landfill gas as a fuel source. Consequently, this invention is a partial solution to what to do with the landfill gas being produced.
U.S. Pat. No. 3,634,051 (Phillips, Jan. 11, 1972) relates to both inorganic metallic and organic amine additives for combustible fuels. More specifically, the reference is concerned with fuel additives that significantly increase fuel economy as well as resulting in more complete combustion and higher flame temperatures. In addition, the additives typically act as corrosion and sulfation inhibitors in a fuel mixture, thereby performing a detergent function as well as improving the combustion process. Inorganic compounds of the metal zirconium, including the potassium, sodium, and lithium salts when function as well as improving the combustion process. Inorganic compounds of the metal zirconium, including the potassium, sodium, and lithium salts when present in trace quantities in a fuel mixture can increase fuel economy from about 5 to 20 percent, or more.
U.S. Pat. No. 3,969,237 (Andress, Jr., Jul. 13, 1976) relates to organic compositions and, relates more particularly to organic compositions in the form of liquid and solid hydrocarbon-containing materials which normally tend to react with and corrode copper surfaces under conditions of use. Still more particularly, the reference relates to improved organic compositions in the form of lubricating oils, greases, fuels and solvents, which in their uninhibited state, tend to react with and corrode copper surfaces with which they may come into contact in performing their intended function.
U.S. Pat. No. 4,157,247 (Collins, III et al., Jun. 5, 1979) relates to the removal of impurities from landfill gas. Decomposition of the refuse within a sanitary landfill produces landfill gas which contains methane and impurities. The impurities may include carbon dioxide, water and various hydrocarbons.
Although the concentration of methane in landfill gas varies, methane may comprise about 50 percent by volume of the landfill gas. In some instances, the landfill gas is used without removal of the impurities, and in other instances, the concentration of the methane is increased by removing some, or substantially all, of the impurities. Landfill gas contains chlorinated hydrocarbons in trace amounts, such as 0.02% to 0.03% by volume which produce corrosive hydrogen chloride gas.
U.S. Pat. No. 4,384,552 (Landers et al, May 24, 1983) relates to gas producing and handling systems and to such systems which produce a combustible gas for burning in an internal combustion engine coupled to an electrical generator.
There are presently many instances where a combustible gaseous fuel, such as methane, is produced as a by-product of other processes, such as in anaerobic digesters. It has long been known that anaerobic digesters can be utilized in decomposing organic waste, such as animal manure, so that the resulting decomposed matter is less offensive and less damaging to the environment. Anaerobic decomposition produces various gaseous by-products including carbon dioxide and combustible methane gas.
A major problem encountered in attempts to utilize the methane gas produced by the digester concerns the need to store the gas when the total amount of gas being produced by the digester is either not used fully by the various appliances utilizing the gas or is not being combusted in the internal gas engine for driving the electrical generator.
This reference is directed to a gas producing and handling system allowing a user to consume all of the gas produced by a variable production supply reservoir in an internal combustion engine coupled to an electrical generator.
U.S. Pat. No. 4,409,102 (Tanner, Oct. 11, 1983) relates to a method for purifying methane gas of a stream constituted of methane gas, carbon dioxide, and, perhaps, hydrogen sulfide. The reference effects purification of the stream to get high quality methane by passing the stream to be purified into contact with water to absorb the contaminants. This absorption step is undertaken within a prescribed pressure range corresponding to pressure required for desired purity in view of the limitations of the water flow rate and time of contact of the water stream and the stream being purified. The feed stream is compressed to the pressure at which absorption takes place. No purified gas leaves the system until the pressure in the absorber has been reached and consequential methane purity assured.
U.S. Pat. No. 4,566,278 (Force, Jan. 28, 1986) relates to a method and system for improving the quality of digester methane gas to enable it to be used effectively and efficiently as a fuel for internal combustion engine--generator systems.
Digester methane gas is generally comprised of a mixture of methane (50-70%), carbon dioxide (30-50%) and varying lesser amounts of oxygen, nitrogen, water, ammonia, hydrogen sulfide and mercaptans and such gas may have a heating value of 400-500 Btu per cubic foot. Although it is possible to bum raw digester methane in internal combustion engines, the efficiency of such engines is drastically reduced from that achieved when pipeline methane (1,000 Btu/ft.sup.3) is utilized.
U.S. Pat. No. 4,904,279 (Kanne et al, Feb. 27, 1990) relates to a hydrocarbon fuel having properties for suppression of particulate emissions during combustion. In particular, the present reference relates to hydrocarbon fuel compositions comprising a hydrocarbon fuel heavier than gasoline containing at least two organically esterified carbonates added thereto to reduce the particulate emissions resulting from the combustion of the hydrocarbon fuel. At least one of the carbonate constituents is of the formula: ##STR1## wherein R.sup.1 and R.sup.2 are the same or different monovalent organic radicals with between 1 and 10 carbon atoms, with the second carbonate compound being a dicarbonate having the general formula: ##STR2## wherein R.sup.3 and R.sup.4 are the same or different monovalent organic radicals with between 1 and 10 carbon atoms.
U.S. Pat. No. 4,906,252 (Gutierrez et al, Mar. 6, 1990) relates to dispersants used in lubricating oil compositions that have the primary function of dispersing particulate materials formed in the engine and keeping those materials in dispersion. As a rule of thumb, the dispersants having the higher molecular weight have higher efficiency in maintaining particulates in dispersion than those with lower molecular weight. Higher molecular weight, however, often causes increased viscosity in the finished formulation. This result may be a benefit in that high temperature lubricating properties are maintained. Increased viscosity may, however, cause increased pumping losses in an engine and result in lower gas mileage. Increased viscosity may, however, cause increased pumping losses in an engine and result in lower gas mileage. Increased viscosity at low temperature may also cause substantial problems in attempting to start engines during the winter. Compositions containing the reference adduct show excellent dispersant capabilities and yet provide superior cold start operation.
U.S. Pat. No. 5,059,405 (Watson et al, Oct. 22, 1991) relates to plants processing landfill gases to produce high BTU methane gas suitable for use in commercial pipelines that generally have a waste gas stream composed of very high purity carbon dioxide gas. There have been problems marketing the waste carbon dioxide for many reasons, not the least of which is its procurement from a source as obnoxious as a landfill. Another equally major problem is the high concentration of corrosive compounds generated from trace components in the landfill gas. These compounds apparently are a common source of the recurring problems involving the short and long term failures of internal reciprocating engines. In order to assure the high quality purity of the carbon dioxide product, any carbon dioxide produced by landfill gases must be subjected to incineration and to the latest filtration, absorption, and scrubbing technologies available.
U.S. Pat. No. 5,034,020 (Epperly et al, Jul. 23, 1991) relates to improving the performance of internal combustion engines utilizing hydrocarbon fuels including gasoline, gasohol and diesel fuel, and, more particularly, to the use of additives and fuels which bum more efficiently and with reduced noxious emissions.
U.S. Pat. No. 5,125,931 (Schulz, Jun. 30, 1992) relates to the disposal of sewage sludge wastes. This reference provides a process for forming briquettes from a mixture of caking coal fines and sewage sludge as principal ingredients and for utilization of the briquettes in a process for the generation of industrially useful products, such as hydrogen, synthesis gas, fuel gas, heat and electrical energy.